Transmission control

ABSTRACT

AN AUTOMATIC TRANSMISSION CONTROL PROVIDING FOR SHIFTING BETWEEN THREE FORWARD DRIVES WHEREIN THERE IS PROVIDED PART ENGINE THROTTLE SEQUENTIAL UPSHIFTING, PART ENGINE THROTTLE DOWNSHIFTING FROM THE HIGH TO THE INTERMEDIATE DRIVE, DOWNSHIFTING FROM INTERMEDIATE TO THE LOW DRIVE AT A PREDETERMINED VEHICLE SPEED AND COAST DOWNSHIFTING FROM THE HIGH DRIVE DIRECTLY TO THE LOW DRIVE AT A PREDETERMINED VEHICLE SPEED.

Dec. 7, 1971 H. E. GHANA TRANSMISSION CONTROL Filed Feb. 24, 1970mmDmmmda U mJDOmIUw .ruim

Dec. 7, 1971 H, E, CHANA 3,625,090

TRANSMISSION CONTROL Filed Feb. 24, 1970 5 Sheets-Sheet 2 2'3 SHIFTVALVE MODULATOR SCHEDULE AND LIMIT VALVE /9/ DETENT VALVE 3-2 DOWNSH IFT TI Ml NG VALVE MAIN LlNE BOOST Low |NTERMED|ATE VALVE TOR @mw dfi/g5jmf@ .m

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MAIN L|NE PRESSURE REGULATOR VALVE /Z l' 95 w /W ya INVENTOR.

INTERMEDIATE SERVO zzz ATTORNEY w Ow f* VACUUM MODULATOR E VALVE UnitedStates Patent C) 3,625,090 TRANSMISSION CONTRUL Howard E. Chana, Flint,Mich., assigner to General Motors Corporation, Detroit, Mich. Filed Feb.24, 1970, Ser. No. 13,718 Int. Cl. B601( 21 /08 U.S. Cl. 74-864 6 ClaimsABSTRACT F THE DISCLOSURE An automatic transmission control providingfor shifting between three forward drives wherein there is provided partengine throttle sequential upshifting, part engine throttle downshiftingfrom the high to the intermediate drive, downshifting from intermediateto the low drive at a predetermined vehicle speed and coast downshiftingfrom the high drive directly to the low drive at a predetermined vehiclespeed.

This invention relates to transmissions and more particularly totransmission controls.

The transmission control according to the present invention is forautomatically controlling a transmission which has a low forward driveestablished by engagement of a one-way type device, an intermediateforward drive which is established by engagement of a friction band typedevice and a high forward drive which is established by engagement of afriction plate type device. The transmission control has shift valveswhich provide for part engine throttle sequential upshifting, partengine throttle downshifting from the high to the intermediate drive anddownshifting from the intermediate to the low drive at a predeterminedvehicle speed. The shift valves also operate to effect a downshift fromthe high drive directly to the low drive to avoid engaging the frictionband type device when the engine throttle is closed and the vehiclespeed reduces to a predetermined value to provide smooth coastdownshifting. The transmission control further includes a sequence valvewhich, by its control over the operation of the shift valve arrangement,assures sequential upshifting through all of the drives.

An object of the present invention is to provide a new and improvedtransmission control.

Another object is to provide a transmission control providing for smoothcoast downshifting.

Another object is to provide in a transmission control a shift valvesystem providing sequential upshifting and downshifting and alsononsequential downshifting for smooth coast downshifts.

Another object is to provide a transmission control having a valvesystem for providing a coast downshift whose smoothness is provided byshifting drive establishment from one drive establishing device toanother without engaging a friction band type device.

Another object is to provide in a transmission control a shift valve andsequence valve arrangement that provides 'for shifting between threedrives including an intermediate drive established by engagement of afriction band type device by part engine throttle sequential upshifting,part engine throttle downshifting from the high to the intermediatedrive, downshifting from the intermediate to the low drive at apredetermined vehicle speed and coast downshifting from the high drivedirectly to the ylow drive at a predetermined vehicle speed.

3,625,090 Patented Dec. 7, 1971 ice These and other objects of theinvention will be more apparent from the following description anddrawing in which:

There is shown a longitudinal sectional view of a transmission drivetrain in FIG. 2 and a schematic of a hydraulic control system accordingto the present invention for controlling this transmission drive trainwhen FIGS. 2, 3 and 4 are arranged in accordance with the diagram shownin FIG. 1.

FIG. 5 graphically illustrates the shift schedule characteristicsprovided by the control system.

TRANSMISSION DRIVE TRAIN ARRANGEMENT The control system according to thepresent invention is particularly suited for controlling vehicletransmissions of the type shown in FIG. 2 which generally comprises ahydrodynamic torque converter 10 and range unit 12 which cooperativelyprovide three forward drives and one reverse drive between thetransmissons rotary input member 14 and rotary output member 16, thelatter member being a shaft. These drive train components are housed ina transmission housing 18 and in the vehicle installation, the inputmember 14 is driven by the vehicles engine and the output member ,16 isconnected to drive the vehicles propelling wheels.

In the converter 10, the input member 14 serves as a front cover forthis unit and is connected to an impeller cover 20 which together withfront cover 14 enclose a fluid chamber 21. In fluid chamber 21 there areprovided a series of pump vanes 22 carried by cover 20, turbine vanes 24carried by a hub 25 and stator vanes 26 which are supported by areaction hub 28 and disposed between the inner ends of the turbine andpump vanes. Stator vanes 26 are permitted free rotation in only onedirection which is the same direction as the pump and turbine vanes by aone-way brake 29, this direction being the forward direction. One-waybrake 29 is disposed lbetween hub 28 and a sleeve 30 which is splined toa front bulkhead 32 that is bolted to the transmission housing. Onewaybrake 29 which may be of any suitable conventional type prevents reverserotation of stator vanes 26 by the circulating uid in the converter.Turbine hub 25 is splined to the front end of a converter output shaft33 which lextends through sleeve 30 to transmit the converter drive tothe range unit 12. The converter 10 is a three element converter ofconventional type and provides torque multiplication up to couplingspeed and fluid coupling operation thereafter in the drive it providesto the range unit 12. A sleeve shaft 34 surrounds sleeve 30 and iswelded to cover 20 so that it rotates at engine or transmission inputspeed. Sleeve shaft 34 is connected to drive the pump of thetransmissions control system as described in more detail later.

The range unit 12 comprises a front planetary gear set 36 and a rearplanetary gear set 37. The front gear set 36 has a sun gear 38, a ringgear 40 and a carrier 41 carrying a planet pinion 42 meshing with thissun gear and ring gear. The carrier 41 is splined to the front end ofoutput shaft 16. The rear gear set 37 comprises a sun gear 44 integralwith sun gear 38 of the front gear set, a ring gear 45 which is splinedto output shaft 16 and a carrier 46 carrying a planet pinion 48 meshingwith this sun gear and ring gear.

Describing now the drive establishing devices of the range unit 12 whichestablish the drives, the converter output shaft 33 which serves as thepower input to the range unit 12 is splined to a clutch drum 49 of aforward drive clutch 50. The forward drive clutch 50 has clutch plates51 that are splined to drum 49 and are adapted to engage clutch plates53 that are splined to a hub 54 which is integral with ring gear 40 offront gear set 36. The plates 51 and 53 are engaged upon admission ofuid pressure to a chamber 56 formed between drum 49 and a piston 57. Arelease spring 58 biases piston 57 towards its clutch release position.

The converter output shaft 33 also drives a clutch hub 60 of a high andreverse clutch 61, the clutch hub 60 being integral with drum 49 whichis splined to shaft 33. The clutch 61 has clutch plates 62 splined tohub 60 that are adapted to enga-ge clutch plates 63 splined to a drum 64which is connected to sun gears 38 and 44 by a bellshaped member 65. Theplates 62 and 63 are engaged upon admission of fluid pressure to eitherone of two chambers 66 and 67 which are formed between drum 64 and apiston 68. A release spring 69 biases piston 68 towards its clutchrelease position. a

An intermediate brake 70 grounded to transmisslon housing 18 is of theband type and is adapted to engage drum 64 by operation of a servo 73which -is shown in FIG. 4. In servo 73, a piston 74 separates an applychamber 75 from a release chamber 76. Piston 74 is mounted on a pistonrod 77 for limited axial movement, the rod 77 being adapted at its leftend to transmit the servos output force to apply or engage band brake70. Upon admission of uid pressure to apply chamber 75, an inner spring78 lightly cushions the transfer of the apply force from the piston -tothe piston rod during initial movement of the piston while an outerspring 80 provides a release force. When the fluid pressure admitted toapply chamber 75 is also admitted to release chamber 76, the spring 80releases the brake engagement since the opposing pressure forces onpiston 74 are equal.

A one-way brake 81 which may be of any suitable conventional type isgrounded to transmission housing 18 and operates to prevent reverserotation and permit forward rotation of a drum 82 that is connected tocarrier 46 of the rear gear set 37. In addition to this holding of thecarrier 46, there is provided a low and reverse brake 84 of the bandtype which is grounded to transmission housing 18 and is adapted toengage drum 82 upon admission of uid pressure to an apply chamber 85 ofa low and reverse servo 86 which is shown in FIG. 4. Fluid pressure inchamber 85 acts on a piston 88 which is mounted on a piston rod 89 forlimited axial movement, the rod 89 being adapted at its upper end totransmit the servos output force to apply or engage band brake 84. Aninner spring 90 lightly cushions the apply force from the piston to thepiston rod during initial movement of the piston while an outer spring91 provides a release force.

The above described transmission drive arrangement is operable toprovide three forward drives and a reverse drive. For neutral operation,all of the drive establishing devices are released.

For the rst or lowest speed range forward drive, only forward driveclutch 50 is engaged to transmit converter drive to ring gear 40 of thefront gear set 36. The transmission drive arrangement in this conditionhas the oneway brake 81 preventing reverse rotation of carrier 46 of therear gear set 37 so that the transmission output shaft 16 is driven inthe forward direction and at a reduced speed by compound action of -gearsets 36 and 37. The low and reverse brake 84 may be engaged for lowdrive to prevent forward rotation of carrier 46 and thereby provide forreverse power ow through t-he range unit 12 to permit engine brakingduring vehicle coasting. The second or intermediate speed range forwarddrive is established by engaging both forward drive clutch 50 andintermediate brake 70. In the intermediate speed range forward drivewith the converter drive to ring gear 40 of the front gear set 36 andthe sun gear 38 of this gear set braked, the transmission output shaft16 is driven in the forward direction at a reduced speed and in a speedrange higher than that obtainable in the low forward drive. The third orhighest speed range forward drive is a direct drive and is establishedby engaging both the forward drive clutch 50 and the high and reverseclutch 61. This locks up the front gear set 36 so that there is provideda 1:1 or direct speed ratio drive between the input and output of rangeunit 12'. The reverse drive is established by engaging the high andreverse clutch 61 and the low and reverse brake 84. With converter driveto sun gear 44 of the rear gear set 37 and with the carrier 46 of thisgear set braked, the transmission output shaft 116 is driven in thereverse direction at reduced speed.

TRANSMISSION CONTROL SYSTEM The present invention is embodied in thetransmission control system shown in FIGS. 2, 3 and 4 which is adaptedto control transmission drive arrangements of the type shown in FIG. 2and described above. Generally, the transmission control system isoperable to establish the transmission in neutral and park conditionsand to provide three selective forward range conditions providingdifferent modes of operation and also to provide a reverse drivecondition.

PUMP

The uid such as oil used in the control system is returned to a sump 94via various exhausts in the systems components, the sump being securedto the underside of the transmission housing 18. Fluid pressure for thecontrol system is supplied by a positive displacement pump 95 of theinternal-external gear type which is housed in a space 96 provided inthe front bulkhead 32. The pumps drive gear 98 (external toothed gear)is keyed to shaft 34 so that the pump is driven when the vehicles engineis running. The engine driven pump 95 draws uid from sump 94 through anintake line 99. Fluid is delivered from pump 95 to a main line 100. Mainline 100 is always connected to deliver fluid to a main line pressureregulator valve 102, an accumulator 103, a modulator valve 104, amodulator trim valve 106, a main line boost low and intermediate val've107, and a manual val-ve 108.

MANUAL VALVE The manual valve 108 determines the operation of thecontrol system and thus that of the transmission drive arrangement andcomprises a spool valve element 110 having spaced lands a, b, c, d and eof equal diameter located in bore 111 of the valve body. The valveelement 110 is movable to six positions which are Park (P), Reverse (R),Neutral (N), Drive range (D), intermediate range (L2) and low range(L1). The valve element 110 is adapted at its left end to be operatedthrough suitable conventional linkage by the operator of the vehicle whomanually selects the valves position.

When the valve element 110 is in the D position as shown, main line isconnected between lands c and d to a drive range line 112 and also to aboost line 114. When valve element is moved to the L2 position, mainline 100 remains connected to drive range line 112 and is in additionconnected between lands d and e to an intermediate range line 115 whileland c now blocks the main line 100 from boost line 114. When valveelement 110 is moved to the L1 position, the main line 100 remainsconnected to both the range line 112 and the intermediate range line115, the latter connection now being provided between lands c and d, andthe main line 100 is in addition connected between lands c and d andthen between lands d and e to a low range line 116 while the boost line114 remains blocked from the main line 100 by land c. When valve element110 is moved to the N position, the main line 100 is connected betweenlands c and d to boost line 114 and is blocked from all other passagesleading from this valve. When valve element 110 is moved to the Rposition, the main line 100 remains connected to boost line 114 and isin addition connected between lands c and d to a reverse apply line 118which has a ow restriction 119 and is directly connected to chamber k66of the servo motor that engages the high and reverse clutch 61. Whenvalve element 110 is moved to the P position, the main line 100 isblocked by land e so that main line pressure is prevented from reachingany of the passages in the valve.

Two exhausts 122 and 123 are connected to bore 111 of the manual valveas shown so that in the P position, the exhaust 122 is connected to onlythe reverse apply line 118 and boost line 114 While the other exhaust123 is connected to only the low range line 116, intermediate range line115 and drive range line 112. In the R position, exhaust 122 is blockedby land c while exhaust 123 is connected to only the low range line 116,intermediate range line 115 and drive range line 112. In the N position,the exhaust 122 is connected to the reverse apply line 118 while exhaust123 is connected to only the low range line 116, intermediate range line115 and drive range line 112. In the D position, the exhaust 122 isconnected to only the reverse apply line 118 while the exhaust 123 isconnected to the low range line 116 and the intermediate range line 115.In the L2 position, the exhaust 122 is connected to only the reverseapply line 118 and boost line 114 while the other exhaust 123 isconnected to only the low range line 116. In the L1 position, theexhaust 122 is connected to only the reverse apply line 118 and boostline 114 While exhaust 123 is blocked from all the uid passages by lande.

GOVERNOR VALVE A governor valve 124 has a driven gear 126 adapted tomesh with a drive gear 127 secured to the transmission output shaft 16.The governor valve 124 is preferably of the type disclosed in U.S. Pat.No. 2,762,384, issued to M. S. Rosenberger and receives fluid from thedrive range line 112 and operates to provide in a governor line 129 agovernor pressure `which increases with increasing vehicle speed. For amore detailed description of the operation of the governor valve,reference may be made to the aforementioned Rosenberger patent.

MODULATOR VALVE Modulator valve 104 provides a pressure which is afunction of engine torque. Modulator valve 104 is controlled by a vacuummodulator 130 which is connected to the engines intake manifold througha nipple 131 and a tube which is not shown. Vacuum modulator 130 ispreferably of the type disclosed in U.S. Pat. No. 3,295,- 388 issued toR. C. Groves and provides a leftwardly acting modulator output force onan output member 133 which force increases with increasing engine torqueas indicated by intake manifold pressure and is corrected for changes inengine torque resulting from changes in ambient atmospheric pressure.For a more detailed description of the operation of the vacuummodulator, reference may be made to the aforementioned Groves patent.

The modulator valve 104 comprises a spool valve element 134 havingspaced lands a and b of equal diameter located in bore 135 of the valvebody. Valve element 134 also has a stem 137 engaged by the modulatoroutput member 133 so that the modulator output force biases valveelement 134 leftward. A modulator line 138 is connected to bore 135always between lands a and b and is in addition always connected throughvalve element 134 by a passage 139 having a flow restriction 140 to achamber 141 at the left end of the valve element.

When valve element 134 is in the position shown, the main line 100 isconnected past the edge of land a and between lands a and b to themodulator line 138. Fluid in line 138 is delivered through ilowrestriction 140 to chamber 141 so that pressure builds in this chamberto urge the valve element rightward against the leftward bias ofmodulator 130. With suicient rightward movement of valve element 134,land a blocks main line while connecting the downstream modulator line138 to an exhaust 142. Assuming a constant leftward biasing force frommodulator 130, modulator valve 104 thus provides a regulated pressurewhich will be called modulator pressure in modulator line 138 determinedby this modulator bias. Varying modulator bias varies modulator pressureand thus the modulator valve 104 operates to increase the modulatorpressure in modulator line 138 from Zero at engine idle to a suitablemaximum value with increasing engine torque or throttle opening asillustrated by the dashed line in FIG. 5. An exhaust 143 exhausts borebetween valve element 134 and member 133.

MODULATOR TRIM VALVE The modulator trim valve 106 provides a pressurewhich is a function of both engine torque and vehicle speed andcomprises a spool valve element 146 having spaced and progressivelylarger lands a, b and c located in an accommodating stepped bore 147 ofthe valve body. The governor line 129 is connected to a chamber 148 sothat governor pressure acts rightward on land a of valve element 146.The modulator line 138 is connected through a flow restriction 149 to achamber 150 so that modulator pressure acts leftward on land c of valveelement 146 against the governor bias. A modulator trim line 151 isconnected to bore 147 always between lands a and b. Assuming there is nogovernor pressure, modulator pressure urges valve element 146 leftwardto open main line 100 to deliver uid between lands a and b to themodulator trim line 151. The pressure that builds in modulator trim line1151 which will be called modulator trim pressure acts 0n the unbalancedland b to urge valve element 146 rightward to connect the modulator trimline 151 to an exhaust 152 while land a closes olf main line `100. Thus,the modulator trim pressure is a regulated pressure which is zero atzero modulator pressure and increases with increasing modulatorpressure. Assuming now that governor pressure is present, such pressureadds a rightward bias to valve element 146 opposing the modulatorpressure bias. Thus, the modulator trim pressure provided by themodulator trim valve increases with increasing modulator pressure orengine torque and decreases with increasing governor pressure or vehiclespeed. An exhaust 153 connected to the bore 147 exhausts this borebetween lands b and c of any leakage past these lands.

MAIN LINE BOOST LOW AND INTERMEDIATE VALVE The main line boost low andintermediate valve 107 provides for boosting main line pressure to ahigh value in both low and intermediate range operation. Valve 107comprises a spool valve element -154 having a land a and a larger land bspaced therefrom located in an accommodating stepped bore 155 of theValve body. A spring 157 biases valve element 154 leftward toward aboost position where the main line 100 is connected between lands a andb to the modulator trim line 151 downstream of a flow restriction 158 inthe latter line. The boost line 114 is connected to a chamber 161 sothat pressure from this line acts on land a of valve element 154 to urgeit rightward against the bias of spring 157 toward a non-boost positionwhere the main line '100 is blocked at bore 155 by land a and themodulator trim line 151 is openly connected between lands a and b toIbypass flow restriction 158. The pressure in the modulator trim line151 downstream of flow restriction 158 acts on the unbalanced land b sothat this pressure is maintained at a minimum value for low andintermediate range operation when chamber 161 is exhausted. Thiscontrols the minimum value of main line pressure in line 100y in low andintermediate range operation and also in Park.

7 MAIN LINE PRESSURE REGULATOR VALVE The main line pressure regulatorvalve 102 regulates the pressure in main line 100 and comprises a spoolvalve element 162 having spaced lands a, b and c of equal diameterlocated in a bore 163 of the valve body. Fluid from pump 95 is deliveredvia main line '100 to a valve element I162 always between lands a and band then through a passage 165 having a flow restriction 166 to achamber 167, passage 165 being provided in this valve element. Fluidpressure in chamber 167 acts to bias the valve element 162 upward with aspring 168 assisting this upward pressure bias. Spring 168 is seated ona screw 4169 which is externally adjustable and provides for accurateadjustment of main line pressure.

The upper end of valve element 162 contacts a spool valve element 170having a land a and a larger land b located in an accommodating steppedbore 171 of a cylinder 172 which is retained in the body by a retainingring 174. An exhaust 173 is connected to exhaust the space between valveelements 162 and 170 to prevent hydraulic lock. The valve element 170and cylinder 172 form a chamber 175 which is connected to the modulatortrim line 151 downstream of flow restriction 158 to provide main linepressure boost as described in more detail later. The reverse apply line118l is always connected to valve element 170 between lands a and b sothat fluid pressure from the reverse line may be used to boost main linepressure as described in more detail later.

The valve element 162 is normally biased to the position shown by aspring 176 and with pump pressure supplied to chamber 167, valve element\162 is urged upward by this pressure against the bias of spring 176 toregulate pressure in main line 100 at a value determined by the springbias with the overage being exhausted first between lands a and b to aconverter feed line 177 and then between lands b and c to the pumpintake line 99 on continued upward valve element movement. The converterfeed line 177 is connected to deliver fluid to converter 10 as shown.Fluid is returned from the converter by a line 178 through a cooler 179to lubricate the transmission before being returned to the sump.

The above described main pressure regulation assumes that only springbias is determining main line pressure. Considering now that pressurefrom the modulator trim line 151 acts in chamber 175 on land a of valveelement 170, this Valve element is urged downward and assists the spring176 in controlling main line pressure. In drlve range, this assistingpressure is modulator trim pressure and thus main line pressure is madea function of both engine torque and vehicle speed and is thus caused to1ncrease with increasing engine torque and decreasing 'vehicle speed. Inlow and intermediate range, this assistmg pressure is maintained above aminimum value and thus main line pressure is maintained above amlnlmumwalue which will be called a boosted value. In reverse, mam l1nepressure in reverse apply line 1118 acts on the unbalanced area of landb of valve element 17 0 in addltion to modulator trim pressure acting onland a to boost main pressure in main line 100 to the highest boostedvalue.

DETENT VALVE A detent valve 180 provides for forced downshifting andalso controls conditioning of the shift schedule. Valve 180 comprises aspool valve element 181 havlng spaced lands a, b and c of equal diameterlocated in a bore 182 of the valve body. A spring 183 normallyyieldingly holds valve element 181 in the position shown which will becalled the normal position. The boost line 114 is connected to a chamber184 at the right end of valve element 181 and this chamber is alwaysconnected through a passage 185 having a flow restriction 186 to achamber 187 at the left end of the valve element, passage 185 beingprovided in the valve element. A solenoid valve 189` has a poppet valveelement 190 which, when the solenoid is deencrgized as shown, is springbiased to close an exhaust port 191 to chamber 187. In that condition,any pressure from boost line 114 delivered to chamber 184 also builds inchamber 187 to permit spring 183 to hold valve clement 181 in the normalposition since the valve element is pressure balanced. In this positionthe boost line 114 is blocked by land c from a limited feed line 194,the modulator line 138 is connected between lands b and c to the limitedfeed line 194, a limited modulator line 195 is blocked by land a and adentent line 197 is connected between lands a and b to an exhaust 198.When solenoid valve 189 is energized, the poppet Valve element 190 ismoved to open exhaust port 191 so that pressure cannot build in chamber187 Then, pressure from boost line 114 acting on land c will move valveelement 181 leftward to a detent position since the valve element is nowpressure unbalanced. In the detent position, the boost line 114 isconnected past land c to the limited feed line 194, the modulator line138 is blocked between lands b and c, the exhaust 198- is blocked byland b and the limited modulator line 195 and detent line 197 areconnected between lands a and b.

The solenoid valve 189 is controlled by an electrical circuit 201 whichmay utilize the vehicle storage battery 202 as a power source and has aswitch 203 which is normally open. An accelerator or throttle pedal 205which controls the engines throttle valve is arranged so that when it ismoved near a position corresponding to wide open engine throttle orthrough dentent, it closes the switch 203 to complete the circuit toenergize solenoid valve 189.

MODULATOR SCHEDULE AND LIMIT VALVE A modulator schedule and limit valve206 provides a pressure in limited modulator line 195 for controllingshifting this pressure hereinafter being called modulator shift schedulepressure and illustrated by the solid line in FIG. 5. This valvecomprises a spool valve element 208 having a land a and a larged land bspaced therefrom located in an accommodating steps portion of a bore 209in the valve body. This valve also has another spool valve element 210having a spaced lands a and b of equal diameter located in an unsteppedportion of bore 209. The valve elements 208 and 210 are normally urgedapart by a spring 213 to their extreme outward positions as shown whichwill be called the valves light engine throttle condition since it willoccur during light engine throttle operation as described in more detaillater. In this condition the limited feed line 194 is connected betweenlands a and b of valve element 208 to a modulator schedule line 214. Inaddition, the modulator schedule line 214 is connected between lands aand b of the other valve element 210 to the limited modulator line 195,the drive range line 112 is blocked by land a of valve element 208 andan exhaust 216 is blocked by land b of the other valve element 210. Anexhaust 217 is always connected to exhaust fluid from between the valveelements 208 and 210 to prevent hydraulic lock. The limited modulatorline 195 is always connected between lands a and b of valve element 210through a flow restricting passage 220 therein to a chamber at the upperend of valve element 210. The spring 213 has a bias which is largeenough so that when the engine is operating at light throttle, it holdsvalve element 210 in its uppermost or light throttle position againstthe modulator pressure in chamber 221 supplied from the modulator line138 via limited feed line 194 and modulator schedule line 214. Thus themodulator shift schedule pressure delivered to the limited modulatorline 195 in this valve condition is equal to modulator pressure asindicated between points A and B in FIG. 5. The limited feed line 1194is also connected to a chamber 222 so that modulator pressure acts onland b of valve element 208 to urge this valve element upward. At apredetermined intermediate modulator pressure which will occur at anintermediate engine throttle opening or engine torque as indicated bythe point B in FIG. 5, this modulator pressure is effective to movevalve element 208 upward against spring 213 to position land b of thisvalve element to close the connection between the limited feed line 194and modulator schedule line 214 while providing for connection of thedrive range line 112 to the modulator schedule line 214 between lands aand b with continuing upward valve element movement increasing theopening of this latter uid connection. Pressure in the downstreammodulator schedule line 214 acts on the unbalanced area of land b ofvalve element 208 to urge it downward against the upward bias providedby modulator pressure and thus the valve element 208 now acts toregulate the pressure in the modulator schedule line 214. The pressuredelivered by the modulator schedule line 214 to chamber 221 is still nothigh enough to move valve element 210 downward and thus, above theaforementioned predetermined intermediate modulator pressure themodulator shift schedule pressure in line 195 is obtained from main linepressure supplied by drive range line 112 and is regulated by the actionof valve element 208. This condition of valve 206 will be referred to asits medium engine throttle condition. Since the upward bias on valveelement 208 increases with increasing modulator pressure, the modulatorshift schedule pressure in line 195 increases with increasing enginetorque or engine throttle opening and at a rate faster than modulatorpressure in the modulator schedule and limit valves medium enginethrottle conditions as indicated between point B and C in FIG. 5. Atlfull engine throttle opening through detent, the boost line 114 .isconnected to the limited feed line 194 so that when main line pressureis made available to this line it acts in chamber 222 on land b of valveelement 208 and moves this valve element further upward and against ashoulder 223` In this position, the drive range line 112 is fully openedto the modulator schedule line 214 so that chamber 221 then receivesfull main pressure when it is available from the drive range line 112.The upward bias provided by spring 213 in this position of valve element208 establishes a regulating bias on the valve element 210` to providefor regulating the pressure in the limited modulator line 19S at apressure which may be below full main line pressure. The pressure actingon land a of valve element 210 urges this valve element downward againstspring 213 so that land a closes off the modulator schedule line 214 andthen the limited modulator line 195 is connected between lands a and bof this valve element to an exhaust 216. This condition of valve 206will be referred to as its full or wide open engine throttle throughdetent condition. Thus, a full engine throttle opening through detent,the modulator shift schedule pressure in line 195 as indicated at pointD in FIG. 5 is obtained from main line pressure supplied by drive rangeline 112 and is :regulated by the action of valve element 210 so that itremain at a constant predetermined regulated pressure value.

12 SHIFT VALVE A l-2 shift valve 225 provides for shifting between firstand second or low and intermediate drive and also provides forestablishment of reverse drive. Valve 225 comprises a pair of spoolvalve elements 226 and 227. Valve element 226 has spaced lands a and bof equal diameter, a larger diameter land c spaced from land b and aneven larger diameter land d spaced from land c located in anaccommodating stepped portion of a bore 228 in the valve body 4whichportion is formed by a cylinder as shown. The other valve element 227has spaced lands a, b and c which are progressively smaller located inan accommodating stepped portion of bore 228. The two valve elements 226and 227 are normally biased rightward by a spring 229 to a downshiftposition as shown. In the downshift position, the limited modulator line195 is connected via a port 230 to a chamber 231 where pressure from thelimited modulator line 195 acts on land a to assist spring 229 in urgingthe valve elements rightward. The governor line 129 is connected to achamber 232 at the right end of valve element 227 and is also connectedby this chamber and a passage 233 in valve element 227 to a chamber 234so that governor pressure acts leftward on land c of valve element 227and also acts leftward on the unbalanced land a of this valve element tooppose the downshift bias provided by spring 229 and from pressure inchamber 231. In the downshift position, the detent line 197 is blockedfrom chamber 231 by land a of valve element 226, one branch of thereverse apply line 118 is blocked by land b of valve element 226 and thelow range line 116 is connected between lands b and c of this Valveelement to a low and reverse apply line 235 that is connected to theapply chamber of the low and reverse servo 86. In the downshift positionthere is, in addition, connection of another branch of the reverse applyline 118 between lands b and c of valve element 227 to an intermediateapply line 236 while land b of this valve element blocks the drive rangeline 112 at the valve bore. A third branch of the reverse apply line 118is connected to bore 228 always between the two valve elements 226 and227. The intermediate apply line 236 is always connected through a flowresrtiction 237 to the apply chamber 75 of the intermediate servo 73 anda check valve 238 in parallel with flow restriction 237 provides forrapid iiow from this chamber.

When governor pressure bias is sufficient to overcome the bias of spring229 and any modulator shift schedule or detent pressure bias asdescribed in more detail later, the valve elements move leftwardly to anupshift position. In the upshift position, the limited modulator line isblocked from chamber 231 by land a of valve element 226, the detent line197 is connected between lands a and b of this valve element to chamber231, the reverse apply line 118 is connected between lands b and c ofthis valve element to the low and reverse apply line 235 and the lowrange line 116 is connected to bore 228 between lands c and d of thisvalve element. Also in the upshift condition, the drive range line 112is connected through a flow of restriction 239 and then between lands band c of the valve element 227 to the intermediate apply line 236 whileland c of this valve element blocks this latter line from the reverseapply line 118.

2-3 SHIFT VALVE A 2-3 shift valve 240 provides for shifting between thesecond and third or intermediate and high drive and comprises a pair ofspool valve elements 241 and 242. The valve element 241 has a land a anda larger land b spaced therefrom located in an accommodating steppedportion of a bore 244 in the valve body which portion is formed by acylinder as shown. The valve element 242 has lands a, b and c ofprogressively smaller diameter located in an accommodating steppedportion of bore 244. The limited modulator line 195 is connected to achamber 248 at the left end of valve element 241 so that pressuresupplied from this line acts on land a of this valve element and urgesthe valve elements rightward toward a downshift position, there beingprovided a spring 249 to normally yieldingly hold valve element 242 inthe downshift position as shown. The governor line 129 is connectible bya l-2-3 sequence valve 250 to a chamber 251 at the right end of valveelement 242 and this chamber is connected by a passage 252 in this valveelement to another chamber 253. When governor pressure is made availableto the 2-3 shift valve 24) by the 1 2-3 sequence valve 250, it acts onland c of valve element 242 and also acts on the unbalanced land a ofthis valve element to urge the valve elements leftward toward an upshiftposition against whatever pressure bias exists on valve element 241 andthe bias of spring 249. In the downshift position shown, the detent line197 is blocked from chamber 248 by land z of valve element 241 and thelimited modulator line 195 is connected via chamber 248 and a port 254to valve element 241 between lands a and b. Also in the downshiftposition, land b of the other valve element 242 blocks the drive rangeline 112 while the reverse apply line 118 is connected through a flowrestriction 255 and then between lands b and c of valve element 242 to ahigh apply line 256. The high apply line 256 is connected to chamber 67of the servo that engages the high and reverse clutch 61 and is alsoconnected to release chamber 76 of the intermediate servo 73. Whengovernor pressure is high enough t move the valve elements 2-41 and 242to their extreme leftward position which is the upshift position, thedetent line 197 is connected between lands a and b of valve element 241while the drive range line 112 is connected through a flow restriction257 and then between lands b and c of valve element 242 to the highapply line 256. A ball check valve 258 operates to connect intermediaterange line 115 to bore 244 between valve elements 241 and 242 when thisline is supplied with pressure and, alternatively, operates to connectthe reverse apply line 118 to this same location when the latter line issupplied with pressure.

1-2-3 SEQUENCE VALVE The 1-2-3 sequence valve 250 provides for sequenceshifting and comprises a spool valve element 259 having lands a and b ofequal diameter located in a bore 260 of the valve body. A spring 261normally biases valve element 259 to a shift-permit position as shownwhere it provides a through connection for the governor line 129 to the2-3 shift valve 240 while land b blocks an exhaust 262. The drive rangeline 112 is connected to a chamber 264 at the left end of valve element259 and when drive range pressure is available, it acts on land a tomove the valve element rightward to a shifteprevent position where landa prevents the governor line 129 from delivering governor pressure tothe 2-3 shift valve 240. In the shift-prevent position of the sequencevalve 250 the governor line 129 downstream of this valve is connectedbetween lands a and b to the exhaust 262. The intermediate apply line236 is connected downstream of flow restriction 237 and check valve 238to a chamber 265 at the right end of the valve element 259 so that whenpressure is available in this line, it balances drive range pressure inchamber 264 so that spring 261 is effective to hold valve element 259 inthe position shown.

DOWNSHIFT TIMING VALVE A 3-2 downshift timing valve 266 times downshiftsfrom high drive to intermediate drive and comprises a spool valveelement 268 having spaced lands a and b of equal diameter located in abore 269 of the valve body. The governor line 129 is connected at apoint upstream of the 1-2-3 sequence Valve 250 to a chamber 270 at theright end of valve element 268 so that governor pressure acts on land bto urge the valve element leftward. The valve element 268 is normallybiased rightward by an inner spring 272 to a fast flow rate position asshown where there is provided an open connection between lands a and bin the high apply line 236 in parallel with flow restriction 237 in thisline. The downshift timing valve 266 is a three position valve and whengovernor pressure is suiciently high enough to move valve element 268leftward against the bias of spring 272 to an intermediate ow rateposition where it contacts a spring seat 274, flats 275 on land b arepositioned to provide a flow restriction in parallel with the flowrestriction 237 so that flow through the intermediate apply line 236 isreduced. An outer spring 276 acts rightward on spring seat 274 so that ahigher governor pressure is required to move the valve element furtherleftward since now it must be moved against the added bias of spring276. When valve element 268 is moved by governor pressure to its extremeleft-hand position which will be called its slow flow rate position, theland b is positioned to block the intermediate apply line 236 at bore269 so that only the flow restriction 237 provides restriction to flowin this line.

1 2 ACCUMULATOR The one accumulator 103 is for smoothing an upshift tointermediate drive and also shifting between the intermediate and highdrives. Accumulator 103 comprises a piston 277 having a land a and alarger land b located in an accommodating stepped bore 278 of the valvebody. The accumulator has three separate chambers 280, 281 and 282respectively exposing all of land a, the unbalanced area of land b andall ofland b. A spring 284 normally biases piston 277 to the positionshown. The main line 100 is connected to chamber 280 through a ballcheck valve 285 that is in parallel with a flow restriction 286, thecheck valve 285 providing for rapid lling of chamber 280 and the flowrestriction 286 providing for slow fluid flow therefrom. Main linepressure in chamber 280 acts on piston 277 to assist spring 284 inholding the piston in the position shown. The high apply line 256 andthe intermediate apply line`236 are connected to chambers 281 and 282,respectively." When pressure is made available to the intermediate applyline 236 for an upshift to intermediate drive, fluid rst fills the applychamber 75 of the intermediate servo 73 and chamber 282 and then aspressure begins to build to the main line pressure value, it acts inchamber 282 to move piston 277 against the bias of spring 284 and withescape of fluid from chamber 280 being restricted by the flowrestriction 286, there is provided a gradual buildup of pressure inapply chamber 75. Then when pressure is made available to the high applyline 256 for an upshift to high drive, fluid first fills the chamber 67of the high and reverse clutch 61, the release chamber 76 of theintermediate servo 73 and chamber 281 and then as pressure begins tobuild to the main line pressure value, it acts in chamber 281 on theunbalanced land b and together with the bias of spring 284 moves piston277 to contract chamber 282 which has main line pressure. With theescape of fluid from chamber 282 restricted by flow restriction 239 inthe drive range line 112, there is provided a gradual pressure buildupin chamber 67. The accumulator 103 is then conditioned to smoothreestablishment of the intermediate drive on a downshift in the samemanner as described on an upshift to intermediate drive.

CONTROL SYSTEM OPERATION The control system whose structure has beendescribed above is operable to provide manual selection of park,reverse, drive, and neutral. The control system is also operable toprovide manual selection of automatic shifting between all forwarddrives and just between the intermediate and low drives and alsoprovides for holding the low drive.

PARK POSITION For parking the Vehicle, the operator places the manualvalve 108 in its P position and with the engine idling, the pumpdelivers fluid via main line 100 to the main line pressure regulatorvalve 102, accumulator 103, modulator valve 104, modulator trim valve106, main line boost low and intermediate Valve 107 and the manual valve108. The manual valve 108 in this position blocks the main line from allthe lines leading from this valve and at the Same time exhausts all thelatter lines. Thus, all the fluid pressure operated friction driveestablishing devices are released and there can be no drive through thetransmission. With the engine idling, modulator pressure is zero andthus modulator trim pressure is zero. Since the boost line 114 isexhausted, the main line boost low and intermediate valve 107 isconditioned in its boost condition. The pressure supplied by themodulator trim line 151 to chamber of the main line pressure regulatorvalve 102 is above a minimum high value as determined by spring 157 ofthe main line boost low and intermediate valve 107 and causes regulationof main line pressure at a constant high value. Overage from the mainline pressure regulator valve 102 charges the converter 10 and with theconverter filled, the fluid exiting -therefrom is directed through thecooler 179 and thence to lubricate the friction parts of thetransmission, the fluid after these uses being returned to sump 9'4. Themain line pressure delivered to accumulator 103 acts in chamber 280 toassist spring 284 in holding the accumulator piston 277 in the positionshown and thus ready for later action.

' REVERSE DRIVE POOSITION When the operator moves the manual valve 108to its R position, the main line 100 is then connected to both the boostline 1'14 and the reverse apply line 118. Fluid thus delivered toreverse apply line 118' flows through the flow restriction 119 directlyto chamber 66 of the high and reverse clutch 61 and is also delivered tothe 142 Shift val've 225. The pressure from the reverse apply line 11'8Iacts on land d of valve element 226 to move it against spring 229 to itsupshift position where it connects the reverse apply line 118 betweenlands b and c to the low and reverse apply line 235 which supplies theapply chamber 85l of the low and reverse servo 86. The pressure from thereverse apply line 118 also acts on land a of valve element 227 of the 12 shift valve 225 to assist in holding this valve element in itsdownshift position in which it connects the reverse apply line 118- tothe intermediate apply line 236 that is connected to the apply chamber75 of the intermediate servo 7-3. At the same time, the reverse applyline '118 is connected by check valve 2158 to the 2f3 shift valve 240where its acts on land a of valve element 242 to assist spring 249 inholding this valve element in its downshift position where it connectsthe reverse apply line 118 through the ow restriction 255 to the highapply line 256 which delivers Huid to chamber 67 of the high and reverseclutch 61 and also to the release chamber 716 of the intermediateservo73. Since in the intermediate servo 73` both the apply chamlber 75 andrelease chamber 716 are supplied with pressure from main line 100`simultaneously as above described, the intermediate servo 73 does notengage the intermediate brake 70. Thus, lboth the high and reverseclutch 61 and the low and reverse brake 84 are engaged to establish thereverse drive with both chambers 66 and y67 of the high and reverseclutch 61 being supplied with fluid pressure to provide this clutch witha large torque capacity for the reverse drive. The main line boost lowand intermediate valve 7 is conditioned in its non-boost condition sincemain line pressure is now supplied to boost line 114. Thus, modulatortrim pressure is now made available bypassing flow restriction 158 tothe main line pressure regulator valve 102 Where it acts in charnber17'5 to increase main line pressure with increasing engine torque. Inaddition, main line pressure is also supplied by the reverse apply line118y to act on the unbalanced land b of the main line pressure regulatorvalve element 170 so that main line pressure regulator valve 102regulates main line pressure at its highest values. Since there is nogovernor pressure provided in this position of the manual valve 108, themodulator trim pressure is not a function of vehicle speed. Thus, mainline pressure for effecting reverse drive increases with increasingengine torque and is unaffected by change in vehicle speed which hasbeen found to provide a very satisfactory match between the torquecapacity of the friction drive establishing devices establishing thereverse drive and the torque they are required to handle.

NEUTRAL POSITION When the manual valve 108 is moved to its N position,the main line 100 remains connected to the iboost line 114 while allother lines leading from this valve are exhausted. Thus, the l-Z shiftvalve 225 resumes its normal downshift position so that all of the fluidoperated friction drive establishing devices are again disengaged sothat no drive can be transmitted through the transmission. Since thereverse apply line 118 is now exhausted,

14 the main line pressure regulator valve 102 reserves only modulatortrim pressure to assist spring 176 in controlling main line pressure,the modulator trim pressure again being main line pressure since thereis no governor pressure.

DRIVE RANG-E POSITION When the operator moves the manual valve 108 toits D position, the main line 100 remains connected to the boost line114 and is in addition connected to the drive range line 112. The driverange line 112 delivers lluid at main line pressure directly to chamber56 of the forward drive clutch 50` to engage this clutch and thusestablish the low drive. The drive range line 112 also delivers uid atmain line pressure to the 1 2 shift valve 225, 2-3 shift valve 240,modulator schedule and limit valve i206, l-2-3 sequence valve 250 andgovernor valve 129. Thus, the governor valve 124 is now effective toproduce governor pressure in the governor line 129 and therefore themodulator trim pressure in line 151 provided by modulator trim valve 106will increase with increasing engine torque and decreasing vehiclespeed. Modulator trim pressure operates on the main line pressureregulator valve 1012. to control the main line pressure so that itincreases with increasing engine torque and decreasing vehicle speed.With the vehicle at rest and therefore zero governor pressure, the 1 2shift valve 225 is in its normal downshift position. Main line pressurefrom the drive range line 112 operates on the 1-2-3 sequence valve 250to bias it to its shift-prevent position preventing any governorpressure supply to the 2-3 shift valve 240 which is also in its normaldownshift position. The l-Z shift valve 225 in its downshift positionconnects the intermediate apply line 236 to the reverse apply line 118which is exhausted by the manual valve 108 in this position whileblocking the drive range line '112I at this valve and also connects thelow and reverse apply line 235 to the low range line 116 which is alsoexhausted by the manual valve '108 in this position. Thus, the brake 70is not engaged by the intermediate servo 73 and the braike l84 is notengaged by the low and reverse servo 86. The 2-3 shift valve 240I in itsdownshift position connects the high apply line 256 to the exhaustedreverse apply line 118 while blocking the drive range line 112 at thisvalve. Thus, the high and reverse clutch 61 is not engaged since lbothchambers 66 and 67 are exhausted.

The detent valve '180 is in its normal position exhausting the detentline 197 while connecting the modulator line 1.38 to the limit feed line194. With the engine idling, the modulator schedule and limit valve 206is in its light engine throttle condition and thus the modulator .shiftschedule pressure delivered to limited modulator line 195 is equal tomodulator pressure which is zero at this engine condition as indicatedin FIG. 5 at point A.

With low drive thus established and when the engine is accelerated ibyoperation of the throttle pedal 205, governor pressure is then producedin governor line 129 to urge an upshift of the 1-2 shift valve 2215,governor pressure being prevented at this time from urging an upshift ofthe 2-3 shift valve 240 since the 1-2-3 sequence valve 250 is in itsshift-prevent position. Also with the presence of governor pressure, themodulator trim pressure is then caused to increase with increasingengine torque and decreasing vehicle speed and thus so is the main linepressure. When the upshift governor pressure bias is effective toovercome the downshift bias provided by modulator shift schedulepressure and the spring 229, the yl-Z shift valve 225 is moved to itsupshift condition where it connects the drive range line 112 through theiiow restriction 239 to the intermediate apply line 236 whilemaintaining the low and reverse apply line 23'5 exhausted by connectingthe latter line to the exhausted reverse apply line 118. Thus, the applychamber of the low and reverse servo 86 remains exhausted so that thebrake 84 remains disengaged.

Fluid is delivered from the main line 100 via range line 112 and theintermediate apply line 236 to chamber 282 of the accumulator 103 andchamber 75 of the intermediate servo 73. The cha-mber 281 of accumulator103 and release chamber 76 of intermediate servo 73 are both exhaustedsince the high apply line 256 is connected by 2-3 shift valve 240 in itsdownshift position to the exhausted reverse apply line 118. When chamber282 of accumulator 103 and apply chamber 75 of intermediate servo 73 arefilled with fluid and pressure then begins to build, this pressureacting in chamber 282 urges the accumulator piston 277 against thespring 284 thereby forcing fluid in the chamber 280 through the flowrestriction 286 back into the main line 100, the check valve 285 closingwith this direction of fluid flow. Since the flow restriction 286restricts flow from chamber 280 as the accumulator piston 277 isstroked, there is provided a gradual buildup of pressure in applychamber 75 of the intermediate servo which thereby gradually engages theintermediate brake 70 to establish the intermediate drive, this pressurebuildup continuing until full main line pressure is reached. Pressurebuildup in the inter-mediate apply line 236 also operates on the l-2-3sequence valve 250 to position it in its shift-permit positionconnecting the governor line 129 to deliver governor pressure to the 2-3shift valve 240.

The modulator shift schedule pressure as illustrated in FIG. 5 providesan early shift schedule for light to medium engine throttle openings andthen rapidly extends this schedule with increasing engine throttleopening or engine torque. Thus, at a throttle opening between idle andan intermediate throttle opening as indicated between the points A and Bin FIG. 5, a 1-2 upshift will occur at a predetermined vehicle speed;however this upshift will require a disproportionately higher vehiclespeed at a wider throttle opening because of the change in the rate ofchange between modulator schedule pressure and engine throttle openingor engine torque as shown between points B and C in FIG. 5. It has beenfound that this dual `shift schedule provides smoother shifting byproviding a better match between engine torque, apply pressures andfriction element torques than does a single pressure schedule such aswould be provided by modulator pressure or modulator trim pressure.

When the 1-2 shift valve 225 is in its downshift position and theaccelerator pedal 205 is moved through detent to condition the detentvalve 180 in its detent position, the boost line 114 is connected to thelimited feed line 194 so that the limited modulator line 195 thendelivers maximum modulator schedule pressure to hold the 1-2 shift valvein its downshift position since the modulator schedule and limit valve206 is then in its full engine throttle through detent condition. Thus,the 1-2 shift valve 225 is then provided with the largest availableunshift resisting bias and when vehicle speed increases sufficiently sothat governor pressure overcomes this increased bias, the 1-2 shiftvalve 225 will upshift to establish the intermediate drive as describedpreviously but with this maximum resisting bias thus limiting maxmumvehicle speed in low drive.

When the 1-2 shift valve 225 is in its upshift position, the limitedmodulator line 195 is blocked from chamber 231 of this shift valve andinstead is connected to the detent line 197 which, below wide openengine throttle, is exhausted by the detent Valve 180 since the lattervalve is then in its normal position. Thus, no part throttle 2-1downshifts can occur since there is no modulator shift schedule pressurebias. The 1 2 shift valve 225 will downshift to reestablish the lowdrive when the bias of spring 229 overcomes the governor bias which willoccur at a predetermined vehicle speed. Alternatively, when the 1-2shift valve 225 is in its upshift position and the accelerator pedal 205is in a position corresponding to full engine throttle opening throughdetent to condition the detent valve 180 in its detent position and thusconditions the modulator shift schedule and limit valve 206 in its fullengine throttle through detent condition, the detent line 197 deliversmaximum shift schedule pressure to chamber 231 where it adds to the biasof spring 229 and immediately forces the l-2 shift valve 225 to itsdownshift position. With the 1-2 shift valve 225 again in its downshiftposition, the apply chamber 75 of the intermediate servo 73 is rapidlyexhausted through the check valve 238Hto rapidly release intermediatebrake 70 and thus quick-ly restore the low drive while the othercomponents of the control system are conditioned as before with the1-2-3 sequence valve 250 preventing governor pressure delivery to the2-3 shift valve 240.

When the 1-2 shift valve is in its upshift position establishing theintermediate drive and then when the vehicle speed increases to a speedsuch that the upshift governor pressure bia-s acting on the 2-3 shiftvalve 240 overcomes the modulator shift schedule pressure acting on bothland a and unbalanced land b of the 2-3 shift valve element 241, the 2-3shift valve 240 is moved to its upshift position. The 2-3 shift valve240 in the upshift position connects the drive range line 112 throughflow restriction 257 to the high apply line 256. The 'high apply line256 is then connected via drive line 12 to deliver fluid from the mainline to chamber 67 ofthe high and reverse clutch 61, the release chamber76 of the inter-mediate servo 73 and the chamber 281 of the accumulator103. When these three chambers are lled with fluid and pressure beginsto build, such pressure acts in chamber 67 to engage the high andreverse clutch 6 1, acts in chamber 76 to assist spring 80 in returningthe piston 74 to its release position so that the intermediate servo 73releases intermediate brake 70 and acts in chamber 281 to assist themain line pressure in chamber 280 both the apply chamber 75 of theintermediate servo 73 and the chamber 282 of the accumulator 103 isrestricted by the flow restriction 239 in the drive range line 112, thecheck valve 238 which is located therebetween permitting free :ow inthis direction, there is provided gradual engagement of the high andreverse clutch 61 and disengagement of intermediate brake 70 whichprovides for smooth transition on this upshift to high drive.

The modulator shift schedule pressure operates on the 2-3 shift valve240 like the way it operates on the 1--2 shift valve 225 as previouslydescribed to provide an early shift schedule for light to medium enginethrottle 2-3 upshifts and then extends this 2-3 shift schedule rapidlywith increasing engine throttle opening. When the 2-3 shift valve 240 isin its downshift position and the engine throttle pedal 205 is depressedthrough detent to condition the detent valve in its detent position, the2-3 shift Valve 240 upshifts at a predetermined high vehicle speedaccording to the maximum upshift resisting bias provided by spring 249and the maximum modulator shift schedule pressure which is beingdelivered by limited modulator line 195.

When the 2-3 shift valve 240 is in its upshift position, the limitedmodulator line remains connected to chamber 248 of this valve so thatthere is provided part engine throttle 3-2 downshifting as compared withthe 1-2 shift valve 225 which prevents part throttle 2-1 downshifting asdescribed previously. The 2-3 shift valve 240 downshifts when thedownshift bias provided by spring 249 and the modulator shift schedulepressure exceeds the upshift bias provided by governor pressure. A partthrottle 3-2 downshift occurs at a lower vehicle speed than la 2-3upshift for the same modulator shift schedule pressure or engine torque.This is because the modulator shift schedule pressure acted on both landa and the unbalanced land b of valve element 241 in the downshiftposition and acts only on land a in the upshift position.

When the 2-3 shift valve 240 is in the upshift position and the enginethrottle pedal 205 is depressed through detent to condition the detentvalve 180 in its detent condition and the modulator schedule and limitvalve 206 in its full engine throttle through detent condition, maximummodulator shift schedule pressure acts on both land a and the unbalancedland b of valve element 241 to immediately force the 2-3 shift valve 240to its downshift position to reestablish the intermediate drive, theletlntb line 197 delivering this pressure to unbalanced When a 3-2downshift occurs, the 3-2 downshift timing valve 266 will have -beenbiased Iby governor pressure to establish the desired flow controlmetering area in the 1ntermediate apply line 236 to meter ilow to theapply Chamber 75 of the intermediate servo 73 to establish tl1e lowdrive. At low vehicle speeds, the 3-2 downshift tlmlng valve 266 ispositioned as shown in its fast flow rate. to provide a fast 3-2downshift. At an intermediate Vehicle speed where governor pressure isincreased to a predetermined intermediate value, the 3-2 downshifttiming valve 266 is conditioned in its intermediate ilow rate positionto provide a slower 32 downshift. At a high Vehicle speed where governorpressure is increased to a predetermined high value, the 3-2 downshifttiming valve 266 is positioned in its slow ilow rate position to providean even slower 3 2 downshift. Thus, engagement of intermediate brake 70is timed to release of the high and reverse clutch `61 at threedifferent time rates which decrease with increasing vehicle speed toprovide good operator feel, particularly for forced 3-2 downshifts.

The governor pressure responsive area and spring bias of the two shiftvalves 225 and 240 are selected so that the 1-2 shift valve 225 moves toits downshift position prior to the 2-3 shift valve 240 moving to itsdownshift position when the vehicle is coasting with the engine throttleclosed, the modulator shift schedule pressure be1ng zero in thiscondition. Thus, there is provided a zero engine throttle coastdownshift from the high drive directly to the low drive, i.e. a zeroengine throttle 3-1 downshift. This is desirable since such a 3-1downshift in this drive train arrangement is made from a friction platedevice to a one-way device and thereby avoids downshift clunk which mayoccur on a 3-21 downshift on the 3-2 shift in this sequence which wouldbe from a friction plate clutch to a friction band. When the enginethrottle is opened slightly providing drive torque, the resultingmodulator shift schedule pressure and part throttle downshiftcharacteristics of the 2-3 shift valve 240 result in a normal 3-2 Iandthen a 2-1 downshift. It will also be appreciated that the 1-2-3sequence valve 250, by its control over the delivery of governorpressure to the 2-3 shift valve 240 as described above, prevents a 1 3upshift so that a l-23 upshift sequence is assured. This sequence alsoallows accumulator 103 to be properly1 positioned for the 1-2 and 2-3shifts.

INTERMEDIATE RANGE POSITION When the manual valve 108 is moved to its L2position, the boost line 114 is then exhausted, the drive range line 112remains connected to the main line 100 and in addition the intermediaterange line 115 is connected to the main line 100. The main line boostlow and intermediate valve 107 then connects the main line 100 to themodulator trim line 151 downstream of flow restriction 158 since boostline 114 is exhausted to permit this valve to be moved to its boostposition. Thus, the main line pressure regulator valve 102 thenregulates the main line pressure in main line 100 at a boosted value.Fluid at main line pressure is delivered by the intermediate range line115 and then by check valve 258 to the 2-3 shift valve 240 where it actson land a of valve element 242 to hold this Valve element in itsdownshift position against whatever governor pressure is made availableto chamber 251 of this valve. If the transmission is in high drive withthe 2-3 shift valve 240 in its upshift position prior to such movementof the manual valve 108 to its L2 position, the main line pressure biaswill immediately move valve element 242 to its downshift position thusproviding a 3-2 downshift whereafter the main line pressure bias willthen hold this valve element in its downshift position. Thus, a 2-3upshift is prevented. Otherwise, the control system operates as beforeto provide the low and intermediate drive with automatic shiftingtherebetween as described previously but with main line pressure now ata boosted minimum value.

LOW RANGE POSITION When the manual valve 108 is moved to its L1position, the boost line 114 remains exhausted, both the drive rangeline 112 and intermediate range line 115 remain connected to the mainline and in addition, the 10W range line 116 is connected to main line100. Thus, the main line pressure regulator valve 102 rcontinues toregulate main line pressure at the boosted minimum value. The low rangeline 116 delivers fluid at main line pressure to the 1-2 shift v-alve225 where it acts on unbalanced land d of valve element 226 to hold the1-2 shift valve in its downshift position if this valve is alreadydownshifted or to urge this shift valve to the downshift position if itis upshifted on movement of the manual valve 108 to the low rangeposition whereafter this pressure bias will then hold the downshiftposition. With the 1-2 shift valve 225 in its downshift position, thelow range `line 116 is connected to the low and reverse apply line 235so that the low and reverse servo 86 is operated to engage the low andreverse brake 84. Thus, in the low range, the low drive is establishedby engagement of the low and reverse brake 84 in addition to engagementof the forward drive clutch 50 so that engine braking is made availableby the low drive in this low range.

The above described preferred embodiment is illustrative of theinvention which may be modified within the scope of the appended claims.

I claim:

1. In a transmission control for use with a transmission in a drivetrain of an engine powered vehicle; a plurality of fluid pressureoperated drive establishing means for establishing a plurailty ofdifferent speed range drives by control of iluid pressure deliverythereto; a source of iluid pressure; governor valve means connected toreceive said fluid pressure for providing a governor pressure increasingwith increasing vehicle speed; shift control pressure valve meansconnected to receive said iluid pressure for providing a shift controlpressure increasing with increasing engine torque; a plurality of shiftvalve means responsive to said governor pressure and said shift controlpressure for determining delivery of said fluid pressure to said fluidpressure operated drive establishing means to effect sequentialdownshifting through said drives when there is engine torque demand and,alternatively, to effect nonsequential downshifting when there is noengine torque demand; and sequence valve means for controlling theresponsiveness of one of said shift valve means to said governorpressure to cause said plurality of shift valve means to effectsequential upshifting through said drives when there is engine torquedemand.

2. In a transmission control for use with a transmission in a, drivetrain of an engine powered vehicle; a plurality of iluid pressureoperated drive establishing means for establishing three different speedrange drives by control of iluid pressure delivery thereto; a source offluid pressure; governor valve means connected to receive said fluidpressure for providing a governor pressure increasing with increasingvehicle speed; shift control pressure valve means connected to receivesaid fluid pressure for providing a shift control pressure increasingwith increasing engine torque; a plurality of shift valve meansresponsive to said governor pressure and said shift control pressure fordetermining delivery of said fluid pressure to said fluid pressureoperated drive establishing means to effect sequential downshiftingthrough said three drives when there is engine torque demand and,alternatively, to effect downshifting directly from the highest speedrange drive to the lowest speed range drive when there is no enginetorque demand; and sequence valve means for controlling theresponsiveness of one of said shift valve means to said governorpressure to cause said plurality of shift valve means to effectsequential upshifting through said three drives when there is enginetorque demand.

3. In a transmission control for use with a transmission in a drivetrain of an engine powered vehicle; a plurality of drive establishingmeans including a friction band type device for establishing a pluralityof different speed range drives with said friction band type deviceestablishing an intermediate speed range drive; a plurality of fluidpressure operated means for controlling the operation of said driveestablishing means; a source of fluid pressure; governor valve meansconnected to receive said fluid pressure for providing a governorpressure increasing with increasing vehicle speed; shift controlpressure valve means connected to receive said fluid pressure forproviding a shift control pressure increasing with increasing enginetorque; a plurality of shift Valve means responsive to said governorpressure and said shift control pressure for determining delivery ofsaid fluid pressure to said fluid pressure operated means to effectsequential downshifting through all of said drives when there is enginetorque demand, and, alternatively, to effect downshifting withoutestablishing said intermediate speed range drive when there is no enginetorque demand so that said friction band device is not operated toeffect downshifting when there is no engine torque demand; and sequencevalve means for controlling the responsiveness of one of said shiftvalve means to said governor pressure to cause said shift valve means toeffect sequential upshifting through all said drives when there isengine torque demand.

4. In a transmission control for use with a transmission in a drivetrain of an engine powered vehicle; a source of fluid pressure; governorvalve means connected to receive said fluid pressure for providing agovernor pressure increasing with increasing vehicle speed; shiftcontrol pressure valve means connected to receive said fluid pressurefor providing a shift control pressure increasing with increasing enginetorque; first shift valve means responsive to both said governorpressure and said shift control pressure for controlling delivery ofsaid fluid pressure to effect transmission shifting between a firstspeed range drive and a second speed range drive; second shift valvemeans responsive to said shift control pressure and also responsive tosaid governor pressure when governor pressure is delivered thereto forcontrolling delivery of said fluid pressure to effect transmissionshifting between said second speed range drive and a third speed rangedrive; and sequence valve means for preventing delivery of said governorpressure to said second shift Valve means when said first shift valvemeans is effecting establishment of said first speed range drive andresponsive to the control of fluid pressure delivery by said first shiftvalve means that effects establishment of said second speed range driveto provide delivery of said governor pressure to said second shift valvemeans.

5. In a transmission control for use with a transmission in a drivetrain in an engine powered vehicle; a source of fluid pressure; firstshift valve means for controlling delivery of said fluid pressure toeffect establishment of a first speed range drive in a downshiftposition and, alternatively, to effect establishment of a second speedrange drive in an upshift position; biasing means for normally biasingsaid first shift valve means to its downshift position; second shiftvalve means for controlling delivery of said fluid pressure to effectestablishment of a third speed range drive on moveemnt from a downshiftposition to an upshift position; biasing means for normally biasing saidsecond shift valve means to its downshift position; governor valve meansconnected to receive said fluid pressure for providing a governorpressure increasing with increasing vehicle speed; shift controlpressure valve means connected to receive said fluid pressure forproviding a shift control pressure increasing with increasing enginetorque; said first shift valve means having governor pressure responsivemeans acted on by said governor pressure to provide an upshift bias forbiasing said first shift valve means to its upshift position; said firstshift valve means also having torque demand pressure responsive meansacted on by said shift control pressure only in the downshift positionof said first shift valve means to provide an upshift resisting bias forresisting said upshift bias; said second shift valve means having torquedemand pressure responsive means acted on by said shift control pressureto provide a bias for biasing said second shift valve means to itsdownshift position; said second shift valve means also having governorpressure responsive means that when acted on by said governor pressureprovides an upshift bias for biasing said second shift valve means toits upshift position; both said governor pressure responsive means andboth said biasing means all being determined so that said first shiftvalve means moves to its downshift position before said second shiftvalve means moves to its downshift position when said shift controlpressure is at a value indicating no engine torque demand; and sequencevalve means for delivering said governor pressure to act on the governorpressure responsive means of said second shift valve means only whensaid first shift valve means is in its upshift position.

6. In a transmission control for use with a transmission in a drivetrain of an engine powered vehicle; a source of fluid pressure; firstshift valve means for controlling delivery of said fluid pressure toeffect establishment of a first speed range drive in a downshiftposition and, alternatively, to effect establishment of a second speedrange drive in an upshift position; spring means for normally biasingsaid first shift valve means to its downshift position; second shiftvalve means for controlling delivery of said fluid pressure to effectestablishment of a third speed range drive on movement from a downshiftposition to an upshift position; spring means for normally biasing saidsecond shift valve means to its downshift position; governor valve meansconnected to receive said fluid pressure for providing a governorpressure increasing with increasing vehicle speed; shift controlpressure valve means connected to receive said fluid pressure forproviding a shift control pressure increasing with increasing enginetorque; said first shift valve means having governor pressure responsivemeans acted on by said governor pressure to provide a bias for biasingsaid first shift valve means to its upshift positon; said first shiftvalve means also having torque demand pressure responsive means acted onby said shift control pressure to provide a bias for resisting movementof said first shift valve means to its upshift position; said secondshift valve means having torque demand pressure responsive means actedon by said shift control pressure to provide a bias for biasing saidsecond shift valve means to its downshift position; said second shiftvalve means also having governor pressure responsive means that whenacted on by said governor pressure provides an upshift bias for biasingsaid shift valve means to its upshift position; both said governorpressure responsive means and both said spring means all beingdetermined so that said first shift valve moves to its downshiftposition before said second shift valve means moves to its downshiftposition when said shift control pressure is at its lowest value; andsequence valve means for preventing delivery of said governor pressureto said governor pressure responsive means of said second shift valvemeans in a shift-prevent position and,

alternatively, for establishing delivery of said governor pressure tosaid governor pressure responsive means of said second shift valve meansin a shift-permit position; spring means providing a spring bias forbiasing said sequence Valve 4means to its shift-permit position; saidsequence valve means having pressure responsive means responsive to saidfluid pressure to provide a shift-prevent bias for opposing said springbias to normally hold said sequence valve means in its shift-preventposition; said sequence valve means having additional pressureresponsive means responsive to the fluid pressure delivery thatestablishes said second speed range drive to provide a shift-permit biasfor assisting said spring bias and oppos- References Cited UNITED STATESPATENTS 2,766,639 10/1956 Rosenberger 74-863 X 3,308,677 3/1967 Van Lentet al 74-864 X 3,309,939 3/1967 Pierce, Jr. 74-869 X lo ARTHUR T.MCKEON, Primary Examiner U.S. Cl. X.R. 74-869

